1. Field of the Invention
The present invention relates to a carrier body for exhaust gas catalysts, and more particularly to a metal carrier body including wound, stacked or otherwise layered layers of high-temperature corrosion-proof metal sheets, which form a plurality of channels or passages through which exhaust gas flow.
2. Description of the Related Art
Metal carrier bodies of this type are used, for example, in the exhaust gas systems of motor vehicles. These carrier bodies are exposed to severe alternating thermal stresses, which limit the service life thereof.
Various ways of increasing the elasticity of such carrier bodies and of controlling the compressive and tensile forces have been proposed. Japanese Published Non-Prosecuted Application JP-A 62-83044, corresponding to German Published Non-Prosecuted Application DE-A 35 34 904 discloses a catalyst carrier body which is made up of alternating layers of two dissimilar metal sheets consisting of a first metal sheet with double corrugations and a second metal sheet without any corrugation. In the carrier body of this type, the number of contact points between the two metal sheet is decreased, thereby providing the required elasticity. Japanese Published Non-Prosecuted Application JP-A 6-269683 discloses a catalyst carrier body in which two dissimilar metal sheets forming alternating layers are a first metal sheet with a simple corrugation and a second metal sheet without any corrugation, respectively. According to this known carrier body, at least one of the first and second metal sheets is formed with cutouts or openings. Alternatively, at least one of the first and second metal sheets is divided into a plurality of segments arranged in spaced relationships. In this carrier body, the cutouts or openings or spaces between the segments can control the compressive and tensile forces.
Carrier bodies are known which are wound from alternating layers of two differently corrugated metal sheets. One example is described in U.S. Pat. No. 4,845,073 issued on Jul. 4, 1989 to Cyron. In this known carrier body, the metal sheets have inner and outer surfaces, and the contact points are disposed on the inner surface of the first metal sheet and on the outer surface of the second metal sheet. During winding, the inwardly oriented troughs are synchronized with inwardly oriented troughs of the second metal sheet.
An object of the present invention is to provide a carrier body for exhaust gas catalyst, which, with sufficiently high structural rigidity, has reduced mass to be heated as well as increased effective surface area exposed to exhaust gas.
According to one aspect of the present invention, there is provided a carrier body for exhaust gas catalysts, comprising:
layers of first and second metal sheets defining passages through which gas flows;
said layers having an upstream region and a downstream region, with respect to direction in which gas flows, which are spaced from each other;
said layers having an intermediate region disposed between said upstream and downstream regions;
said first metal sheet being so corrugated as to be brought into contact with said second metal sheet in each of said upstream and downstream regions.
Wherein, in each of said upstream and dowstream regions, said first metal sheet has a first corrugation with first amplitude; and wherein, in said intermediate region, said first metal sheet has a second corrugation with a second amplitude that is less than the first amplitude.